/**
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.dtdream.emr;

import java.sql.Timestamp;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.TimeZone;

import org.apache.hadoop.hive.ql.exec.Description;
import org.apache.hadoop.hive.ql.exec.UDFArgumentException;
import org.apache.hadoop.hive.ql.exec.UDFArgumentLengthException;
import org.apache.hadoop.hive.ql.exec.UDFArgumentTypeException;
import org.apache.hadoop.hive.ql.exec.vector.VectorizedExpressions;
import org.apache.hadoop.hive.ql.exec.vector.expressions.VectorUDFDateDiffColCol;
import org.apache.hadoop.hive.ql.exec.vector.expressions.VectorUDFDateDiffColScalar;
import org.apache.hadoop.hive.ql.exec.vector.expressions.VectorUDFDateDiffScalarCol;
import org.apache.hadoop.hive.ql.metadata.HiveException;
import org.apache.hadoop.hive.ql.udf.generic.GenericUDF;
import org.apache.hadoop.hive.serde2.io.DateWritable;
import org.apache.hadoop.hive.serde2.io.TimestampWritable;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorConverters;
import org.apache.hadoop.hive.serde2.objectinspector.ObjectInspectorConverters.Converter;
import org.apache.hadoop.hive.serde2.objectinspector.PrimitiveObjectInspector;
import org.apache.hadoop.hive.serde2.objectinspector.PrimitiveObjectInspector.PrimitiveCategory;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorFactory;
import org.apache.hadoop.hive.serde2.objectinspector.primitive.PrimitiveObjectInspectorConverter.TimestampConverter;
import org.apache.hadoop.io.IntWritable;

/**
 * UDFDateDiff.
 *
 * Calculate the difference in the number of days. The time part of the string
 * will be ignored. If dateString1 is earlier than dateString2, then the
 * result can be negative.
 *
 */
@Description(name = "datediffmin",
        value = "_FUNC_(date1, date2) - Returns the number of days between date1 and date2",
        extended = "date1 and date2 are strings in the format "
                + "'yyyy-MM-dd HH:mm:ss' or 'yyyy-MM-dd'. The time parts are ignored."
                + "If date1 is earlier than date2, the result is negative.\n"
                + "Example:\n "
                + "  > SELECT _FUNC_('2009-07-30 18:34', '2009-07-31 17:20') FROM src LIMIT 1;\n"
                + "  1")
@VectorizedExpressions({VectorUDFDateDiffColScalar.class, VectorUDFDateDiffColCol.class, VectorUDFDateDiffScalarCol.class})
public class GenericUDFDateDiffMin extends GenericUDF {
    private transient SimpleDateFormat formatter = new SimpleDateFormat("yyyy-MM-dd HH:mm");
    private transient Converter inputConverter1;
    private transient Converter inputConverter2;
    private IntWritable output = new IntWritable();
    private transient PrimitiveCategory inputType1;
    private transient PrimitiveCategory inputType2;
    private IntWritable result = new IntWritable();

    public GenericUDFDateDiffMin() {
        formatter.setTimeZone(TimeZone.getTimeZone("UTC"));
    }

    @Override
    public ObjectInspector initialize(ObjectInspector[] arguments) throws UDFArgumentException {
        if (arguments.length != 2) {
            throw new UDFArgumentLengthException(
                    "datediff() requires 4 argument, got " + arguments.length);
        }
        inputConverter1 = checkArguments(arguments, 0);
        inputConverter2 = checkArguments(arguments, 1);
        inputType1 = ((PrimitiveObjectInspector) arguments[0]).getPrimitiveCategory();
        inputType2 = ((PrimitiveObjectInspector) arguments[1]).getPrimitiveCategory();
        ObjectInspector outputOI = PrimitiveObjectInspectorFactory.writableIntObjectInspector;
        return outputOI;
    }

    @Override
    public IntWritable evaluate(GenericUDF.DeferredObject[] arguments) throws HiveException {
        output = evaluate(convertToDate(inputType1, inputConverter1, arguments[0]),
                convertToDate(inputType2, inputConverter2, arguments[1]));
        return output;
    }

    @Override
    public String getDisplayString(String[] children) {
        return getStandardDisplayString("datediff", children);
    }

    private Date convertToDate(PrimitiveCategory inputType, Converter converter, DeferredObject argument)
            throws HiveException {
        assert(converter != null);
        assert(argument != null);
        if (argument.get() == null) {
            return null;
        }
        Date date = new Date();
        switch (inputType) {
            case STRING:
            case VARCHAR:
            case CHAR:
                String dateString = converter.convert(argument.get()).toString();
                try {
                    date = formatter.parse(dateString);
                } catch (ParseException e) {
                    return null;
                }
                break;
            case TIMESTAMP:
                Timestamp ts = ((TimestampWritable) converter.convert(argument.get()))
                        .getTimestamp();
                date.setTime(ts.getTime());
                break;
            case DATE:
                DateWritable dw = (DateWritable) converter.convert(argument.get());
                date = dw.get();
                break;
            default:
                throw new UDFArgumentException(
                        "TO_DATE() only takes STRING/TIMESTAMP/DATEWRITABLE types, got " + inputType);
        }
        return date;
    }

    private Converter checkArguments(ObjectInspector[] arguments, int i) throws UDFArgumentException {
        if (arguments[i].getCategory() != ObjectInspector.Category.PRIMITIVE) {
            throw new UDFArgumentTypeException(0,
                    "Only primitive type arguments are accepted but "
                            + arguments[i].getTypeName() + " is passed. as first arguments");
        }
        PrimitiveCategory inputType = ((PrimitiveObjectInspector) arguments[i]).getPrimitiveCategory();
        Converter converter;
        switch (inputType) {
            case STRING:
            case VARCHAR:
            case CHAR:
                converter = ObjectInspectorConverters.getConverter(
                        (PrimitiveObjectInspector) arguments[i],
                        PrimitiveObjectInspectorFactory.writableStringObjectInspector);
                break;
            case TIMESTAMP:
                converter = new TimestampConverter((PrimitiveObjectInspector) arguments[i],
                        PrimitiveObjectInspectorFactory.writableTimestampObjectInspector);
                break;
            case DATE:
                converter = ObjectInspectorConverters.getConverter((PrimitiveObjectInspector)arguments[i],
                        PrimitiveObjectInspectorFactory.writableDateObjectInspector);
                break;
            default:
                throw new UDFArgumentException(
                        " datediffmin() only takes STRING/TIMESTAMP/DATEWRITABLE types as " + (i + 1)
                                + "-th argument, got " + inputType);
        }
        return converter;
    }

    private IntWritable evaluate(Date date, Date date2) {

        if (date == null || date2 == null) {
            return null;
        }
        // NOTE: This implementation avoids the extra-second problem
        // by comparing with UTC epoch and integer division.
        // 86400 is the number of seconds in a day
        long diffInMilliSeconds = date.getTime() - date2.getTime();
        result.set((int) (diffInMilliSeconds / (60 * 1000)));
        return result;
    }
}
